Astronomers knew a hunk of debris from an unknown spacecraft was going to slam into the far side of the moon in March, so they got plenty of before-and-after photographs of the surface. Software usually compares the photos, looking for what's changed to tell where the object hit, the New York Times reports. But the photos were taken at different times of day, and the program had trouble with the shadows. So the search went retro. "We just sat down and had several people manually going through the millions of pixels," said Mark Robinson of Arizona State University, lead investigator for the camera on NASA's Lunar Reconnaissance Orbit. What they found deepened the mystery.
The impact left what Live Science describes as an unexpected, "weird double crater." The school says NASA has counted at least 47 NASA rocket bodies that have hit the moon. "No other rocket body impacts on the Moon created double craters," NASA said in a statement. The space junk was going about 5,770 mph when it hit the moon on March 4, punching out overlapping craters, the eastern one 59 feet across and the western one 52.5 feet. There's no photo of the impact, which probably sent a plume of lunar dust hundreds of miles into space. Alexander Sonke, a recent graduate who made the discovery in the photos after staring at them for about 50 hours, said he jumped out of his seat a bit and "had a feeling that this was definitely it."
In trying to figure how it happened, knowing where the object came from would help. There's reason to suspect a Long March 3C rocket launched by China in 2014. But China says that rocket stage burned up after reentering Earth's atmosphere. Some US experts don't buy that, suggesting China is mixing up its rockets. Bill Gray, a US astronomer who's convinced the debris came from China's rocket, hopes this case leads space agencies and companies to do a better job tracking their rockets. Robinson's OK with the double crater being a mystery for now. "It's cool," he said, adding, "That's always way more fun than if the prediction of the crater, its depth and diameter, had been exactly right." NASA posted photos here. (Read more moon stories.)